It's even more simple than comparing big macs to cigarettes. I'm not the model for fitness. I gained a lot of weight my junior/senior year, spent over 12 hours on campus/day, didn't eat all day until late at night, hardly slept... just had a lot on my plate (so to speak). Ended up gaining a ton of weight, which is something I'm still working on losing. //end personalrant.
However, just my opinion... but I think being overweight is better than smoking or drinking. Fat is something natural to the body... and of course, an excess of it is bad... but it's something the body needs. Ethanol and tobacco, on the other hand, are foreign and serve no benefit or use to the body. Even a small bit initially is considered toxic, because it's just not supposed to be in our system.
I don't judge people for smoking/drinking... as long as it doesn't become a detriment to people around them. If my GP decides to drink on the weekends, that's fine with me. I just choose not to do it and never will. But trying to compare being overweight to smoking is just silly, I think.